Only a few of the thermosetting resins that are commonly used today in fiber-reinforced composites generally can be used in high-temperature applications (e.g., aerospace applications). These high-temperature thermosetting resins are undesirable in many applications because they often form brittle composites that have relatively low thermal stabilities.
Recently, chemists have sought to synthesize oligomers for high-performance, high-temperature advanced composites suitable for high-temperature applications. These composites should exhibit solvent resistance, be tough, impact resistant and strong, and be easy to process. Oligomers and composites that have thermo-oxidative stability are particularly desirable.
Imides and many other resin backbones have shown surprisingly high glass-transition temperatures, reasonable processing parameters and desirable physical properties for high-performance, high-temperature composites. However, typical polyimides are susceptible to thermo-oxidative aging that reduces their long-term strength and stiffness. Further, most formulations for high-temperature polymer-matrix composites have monofunctional endcaps which limit the degree of crosslinking that can be attained.
Accordingly, there remains a need in the art for polyimide oligomers having high thermo-oxidative stability with improved crosslinking and composites formed therefrom.